System for detecting hot elements on railway vehicles



LLLW

May 11, 1965 H. c. SIBLEY 3,133,350

SYSTEM FOR DETECTING HOT ELEMENTS ON RAILWAY VEHICLES Original FiledOct. 30, 1959 15 Sheets-Sheet 1 FIG. I.

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I INVENTOR. H.C.SIBLEY HIS ATTORNEY y 1, 1965 H. c. SIBLEY 3,183,350

SYSTEM FOR DETECTING HOT ELEMENTS 0N RAILWAY VEHICLES Original FiledOct. 30, 1959 l3 Sheets-Sheet 2 FIG 6 D' H SSI LM'I \U 1 26 no /NR 8:1 1. WO -W551 woa +-1 Iss2 I LM2 SEE FIG.5

i I R a; 02 E5 c.s. (8+) I e *4 SEE L Rm 7: F u? IG 5 H- r-RECORDE SCRINVENTOR. Y H C SIBLEY n9: BY H'byl- 7 HIS ATTORNEY May 11, 1965 H. c.SIBLEY 3,183,350

SYSTEM FOR DETEC'I'ING HOT ELEMENTS ON RAILWAY VEHICLES Original FiledOct. 30, 1959 13 Sheets-Sheet 5 RECORDER MARKER ANALOG PENS PENS NO. NO.NO. NO. I 2 l 2 H. c. SlBL-EY 3,183,350 SYSTEM FOR DETECTING HOTELEMENTS ON RAILWAY VEHICI ES May 11, 1965 13 Sheets-Sheet 4 OriginalFiled Oct. 30, 1959 an. MU 9 Y a M 2 \s m E m m m l W a M Ill S a ge 3 Cm w fl 9 P9 L. $11 l- 2 m- H h? b F R m ML 2 m 3 g M m 4 1D g B W I T lll w IT wmrlllznllL w r A 2 T T 8 7 WW5 my? a O W D D .x v 2, H .LT 2 E Ev 9 5 M L Mm L 2 PM G G. n5 U 0 F 0 1 AE h mm 8 G 9% m lm i mm W M R May11, 1965 H. c. SIBLEY 3,

SYSTEM FOR DETECTING HOT ELEMENTS ON RAILWAY VEHICLES Original FiledOct. 30, 1959 13 Sheets-Sheet 5 75 7s y Y 65 6 0 E HJE RECORDER l MARKERl ANALOG PENS PENS NO. NO. I NO. NO.

IN VEN TOR.

H.C.S|BLEY HIS ATTORNEY May 11, 1965 H. C. SIBLEY SYSTEM FOR DETECTINGHOT ELEMENTS ON RAILWAY VEHICLES Original Filed Oct. 30, 1959 15Sheets-Sheet 6 DRAGGING BRAKE lQflJ'BL'LL F G 7C 29? 229 F @I |2|4 IGATE 5 R02 i I I 84L 89 I I5? AC. 296 CHOPPER AME w ale-4+) GATEDIIJOEDTE 8% 65E 2S 2S GEN\. 5 l I 90 I g DRAGGING BRAKE DETECTIONCIRCUIT IN VEN TOR.

HIS ATTORNEY May 11, 1965 H. c. SIBLEY 3,183,350

SYSTEM FOR DETECTING HOT ELEMENTS ON RAILWAY VEHICLES Original FiledOct. 30, 1959 l3 Sheets-Sheet 7 FIGTD. -225 I CLEAR CIRCUIT 1 l l I I Ii H I 44 I 313 I I J l E70 INVERTEFITE3 INVEIRTERTIOZ INVENTOR.H.C.SIBLEY Hls' ATTORNEY May 11, 1965 Original Filed Oct. 30, 1959 FIG.8A.

H. c. SIBLEY 3,183,350

SYSTEM FOR DETECTING HOT ELEMENTS ON RAILWAY VEHICLES 13 Sheets-Sheet 8INVENTOR.

H.C.SIBLEY HIS ATTORNEY H. C. SIBLEY SYSTEM FOR DETECTING HOT ELEMENTSON RAILWAY VEHICLES Original Filed Oct. 30, 1959 May 11, 1965 1sSheets-Sheet 9 mohumkmo woo-0 m Ow mum mmvron. H.C. SIBLEY ms A%mmomoowm 2.5016 M l lllll wmo 3/ y 11, 1965 H. c. SIBLEY 3,183,350

SYSTEM FOR DETECTING HOT ELEMENTS ON RAILWAY VEHICLES Original Fil edOct.v 30, 1959 13 Sheets-Sheet 10 FIG. 9A. FIG. 98

I I I I WDI I WDI I I woz W02 I I I W0 3 I I /\I was I I I I II I FF'IJL' FL FFI I I I FFZ I 5 I FF2 I I I I I I Ismsv I I I, I MI, I GA Is II I I I I l I I I I I I I I I I I I I I GA as GA2S I I I I I I I I I .3!I I I x. I I I I I HJS I HJS I was I DBS I I I'- I I II I A.I ."2 m VALAP Ma a MRE ASSUME? ASSUME;-

(IITRAIN MOVING W-E (I) TRAIN MOVING E-W (2) NO HOT JOURNAL (2) ONE HOTJOURNAL (3) NO DRAGGING BRAKES (3) N0 DRAGGINfi-BRARES I VENTO HQEIBLEYHIS ATTORNEY y 1, 1965 H. c. SIBLEY 3,183,350

SYSTEM FOR DETECTING-HOT ELEMENTS ON RAILWAY VEHICLES Original FiledOct. 30/1959 13 Sheets-Sheet ll l l GAIS L feAzs HJS DBS

. i p'fi I I l M.'R"2 I L ASSUME? (I) TRAIN MOVING W-E 2) NO HOT JOURNAL(3) DRAGGING BRAKES INVENTOK HIS ATTORNEY y 11, 1965 H. c. SIBLEY3,183,350

SYSTEM FOR DETECTING HOT ELEMENTS ON RAILWAY VEHICLES Original FiledOct. 30, 1959 1s Sheets-Sheet 12 r" 2 m a E,------+ I a: LU 2 LU 8 a:

(E: 2 mm a i g 5 if I l A 0 5 i Z g lt- 2 INVEVTOR.

HIS ATTORNEY FIG IO.

H. C. SIBLEY May 11, I965 SYSTEM FOR DETECTING HOT ELEMENTS ON RAILWAYVEHICLES 13 Sheets-Sheet 13 Original Filed Oct, 30, 1959 Jlii IL 538mm E&Y .m: .mE fimm v 5w 5 N 9E m 1mm HIS ATTORNEY United States Patent 0SYSTEM FOR DE'IECTENG HOT ELEMENTS 0N RAHJWAY VEHICLES Henry C. Sibley,Rochester, N.Y., assignor to General Signal Corporation Continuation ofapplication Ser. No. 849,889, Oct. 30, 1959. This application Feb. 9,196b, Ser. No. 7 ,72'7 8 Claims. (Cl. 246-169) overheating of thebearings of railway cars, particularly freight cars. Although frequentinspections are made and bearings are regularly lubricated, it is stilla relatively frequent happening for a journal to become overheated to asuflicient extent that the car itself may catch on lire or there may beviolent, intermittent seizures of the axle so that it is eventuallysheared ofl. Since a high standard of inspection and maintenance has notbeen able to reduce the resulting damages to a satisfactory level, ithas become necessary to resort to means which will detect an incipientoverheated bearing condition and provide a warning thereof before thecondition becomes dangerous.

Another condition frequently resulting in damage occurs as the result ofthe inadvertent dragging of the brakes. Although the brakes on the trainmay be properly released by the trainman, it nevertheless sometimesoccurs that the brakes on a single wheel or, even more often, all thebrakes on a particular truck, are actually not released but are insteadtightly held against the Wheels, sometimes to such an extent that thewheels are entirely prevented from rotating. The consequent sliding ofsuch wheels not only causes flat spots to develop thereon, but alsoincreases the possibility of derailment. Where the dragging brakes arenot so tightly clamped against the wheel so as to stop rotation, thereis nevertheless a great amount of heat generated by the dragging of thebrakes and this may be transmitted through the wheel to its hub, andthence over the axle to the journal, where it may result indeterioration of the lubricant so that a hot journal box may resulttherefrom.

With respect to the problem of detecting overheated journals, variousexpedients have been devised in an attempt to solve this problem. Morerecently, these atem-pts have taken the form of providing a radiationdetection device alongside the trackway. This device may comprise abolometer sensitive to infrared rays or a thermocouple. The generalpractice is to scan the successive journal boxes themselves with theradiation detection device in such a manner that an output signal isderived for each passing journal whose amplitude is proportional to thejournal box temperature. Associated equipment is responsive to thisoutput signal and provides a distinctive signal, either visual oraudible, to indicate the presence of an overheated journal. Suchequipment has been found to have real merit, but experience with itindicates that there are, nevertheless, several shortcomings connectedwith it. 'For example, under certain conditions an overheated journal isnot detected by the equipment. At other times, an indication of anoverheated journal will be given when there is, in fact, no overheatedjournal at all, and this sort of error, although on the side of safet isnevertheless detrimental in that unnecessary stopping of railway trainshas a highly adverse eltect 3&83359 Patented May 11, 1965 upon operatingcosts. It is additionally a characteristic of these prior systems thatthey do not provide any detection of dragging or locked brakes.

In view of these several drawbacks of the detection 7 systems of theprior art, it is proposed by this invention to provide a system for thedetection, not only of overheated journals, but also of dragging orlocked brakes. As will be seen, the added function of dragging brakedetection uses in common much of the equipment used for the detection ofoverheated journals so that consid era'ble economy of equipment results.In addition, a considerable increase in reliability of detection ofoverheated journals is experienced through use of the present invention.

Described briefly, it is contemplated to provide a radiation detectiondevice, or radiometer, which is p0- sitioned alongside the track railand is so located and directed that it scans the infrared radiationlevel of each wheel hub rather than the journal itself. Whenever thereis an overheated journal, the heat is conducted away from the journalbox wherein it is generated, over the axle to the hub of the wheel, andto the body of the Wheel which tends to act as heat sink.Experimentation has shown that even an incipient overheated journalcondition will result in' an appreciable rise in temptrature of thewheel hub above ambient temperature. Scanning the successive wheel hubsrather than the journal boxes produces several distinct and importantadvantages.

One of these advantages results from the fact that the bearings of a carequipped with roller bearings normally run at nearly the sametemperatures as the bearings of the more common type of freight carhaving the slidingbearing type of construction. However, the journalboxes for the roller bearings are so constructed as to more readilyreceive the heat generated in the journal and dissipate it to theoutside than does the construction of the journal boxes for the plane orsliding type bearings. Because of this, the scanning of journal boxesfor roller bearings under normal conditions tends to give unreliableinformation since each such journal box tends to provide a higher levelof output signal from the radiometer than is produced by scanningjournal boxes of sliding type bearings under normal conditions and thusgives an erroneous hot journal indication. Although various expedientshave been devised in an attempt to overcome this problem, none hasproved entirely successful. On the other hand, the scanning of the wheelhubs rather than the journal boxes as contemplated by' the presentinvention completely eliminates this problem since it has been foundthat the wheel hub of a roller bearing equipped car is not substantiallydifferent in temperature than the usually sliding type bearing.

Another distinct advantage which is derived from scanning the Wheel hubrather than the journal box is the abality to scan also the wheel rimsand the brakes. Thus, by directing the angle of scan toward the wheelhub and across the plane of the wheel, the angle of scan will not onlyscan each Wheel hub, but will as Well scan the face of the wheeloutwardly of the hub including the wheel web or plate and also the wheelrims and even the brake shoes as will subsequently be seen. Theforegoing results are achieved,.as already described, in part by sopositioning the radiometer and directing its angle of scan that it scanseach wheel hub, and by also directing the scanning beam across the planeof the wheel at a level such that each wheel rim and also each brakeshoe subtend the scanning angle of the radiometer.

it has been known in the art that inside wheel hubs might be scanned toobtain thereby indications as to the temperatures of the respectivejournals. However, it has been believed necessary, in systems wherewheel hub scanning has been contemplated, to direct the scanning beam QBgenerally parallel to the track rails, and this has the considerabledisadvantage that two scanning devices are then required on each side ofthe trackway, one for each direction of train travel. Alternatively, ithas been contemplated to use but a single scanning unit, but to directits beam of scan directly upwards toward inside axles. Then, only oneunit is required for both directions of travel, but this arrangement hasthe attendant disadvantage of placing the viewing window in a horizontalposition so that dirt and snow readily obscure it. In the presentinvention, by contrast, the beam of scan is in a plane generallyperpendicular to the track rails and directed upwardly across the planeof the wheels, making an angle of about forty degrees to the horizontal.Because of this, none of the above disadvantages are encountered sinceonly one radiometer unit is needed for both directions of travel and yetthe viewing window is at an angle such that it is well protected fromdirt or snow accumulations. Moreover, when wheel hub scanning has beenpreviously contemplated, it has been thought to be necessary that theradiometer be placed between the track rails and directed toward the hubon the inside of each wheel rather than the outside. Tests have shownthat there is a considerable disadvantage in such an arrangement becauseof the considerably longer time required for journal heat to travel tosuch inside hub thereby introducing a considerable delay in theindication of an abnormal condition and also because of the considerablylower temperatures of the inside wheel hub which makes it difficult toobtain radiation readings.

In addition to positioning the radiometer as described above, it ispreferably so positioned and directed that its angle of scan is alsosubtended by each coupler between successive cars. The object of doingthis is to prevent the radiometer from scanning the sky betweensuccessive cars and particularly to prevent its receiving directradiation from the sun since this might cause serious damage to thedevice. This permits directing the radiometers beam of scan upwardlywhile, at the same time, obviating the need for a fast-acting shutterwhich will close between successive cars.

Another advantage of scanning the hubs of the wheels is that they aregenerally very well sheltered from the direct rays of the sun; whereas,the journal boxes covering the journals extend beyond the frame of thetrucks and do receive the direct rays of the sun. When the direct raysof the sun are on the journal boxes of one side of a car and not theother, such condition tends to produce signals indicative of overheatedjournals although such is not the case. Thescanning of the outside hubsof the wheels minimizes this effect considerably.

Because of the desire to scan not only successive wheel hubs with asingle radiometer but also wheel rims, means must be employed todifferentiate between the different signals received from the diiierentsources of radiation. This is accomplished by a novel gating circuitorganization which distinguishes between the signals received by asingle radiometer from a wheel hub and associated brake shoe so thatseparate distinctive indications can be given for the overheated journalcondition and the dragging brake condition. It is, of course, desiredthat the same equipment be effective for either direction of travel ofthe train. This poses additional problemswhich will be more apparentfrom the detailed description that follows since the gating circuitsmust recognize that the train is traveling in one particular directionor the other and control the gating circuits accordingly so that therespective signals from wheel hubs and wheel rims do not becomeintermixed and produce erroneous output information.

It has already been described that the wheel hub becomes readilyoverheated when there is an overheated journal. It is also plausible,therefore, that an overheated journal condition would as well result inan overheating of the wheel rim, and experiments have indicated thatthis does indeed occur. For this reason, merely scanning a wheel rim anddetecting that its temperature is more than some predetermined amountabove ambient is not sufficient to give a reliable indication of adragging brake condition since such temperature rise might also havebeen caused by an overheated journal condition. To eliminate thisambiguity, the present invention incorporates comparison means whichcompares the infrared radiation level derived from the wheel rimascompared to that derived from the'wheel hub for the same wheel. Thiscomparison circuit is so organized that a dragging brake condition willbe given only when the signal obtained from the wheel rim exceeds by apredetermined amount the signal obtained from the wheel hub. Thus, ifthe elevated rim temperature has come about as a result of an overheatedjournal condition, it must necessarily be true that the Wheel hub is ata higher temperature than the wheel rim; in that event, no draggingbrake detection signal is given. However, when the opposite conditionsobtain, i.e. the wheel rim is at a higher tern erature than the wheelhub, this is a quite certain indication that the elevated temperature ofthe wheel rim has come about as a result of a dragging brake condition.

Each radiometer is provided with a protective shutter mechanism whichnormally prevents infrared radiation from impinging upon the detectorelement. This shutter is opened when detection apparatus at theradiometer location indicates that a train is present. Ordinarily, theshutter remains open after the train has passed the radiometer locationuntil an associated track circuit becomes unoccupied. There may be somelapse of time after the last car of the train has passed the radiometerlocation before the track section becomes unoccupied, and this isparticularly true, of course, if the train should stop in the tracksection after having passed the radiometer location. Under thesecircumstances, it is desirable that the shutter be closed in the eventthat any high level of radia-' tion is being directed onto the infrareddetector. For this purpose, a light sensitive cell is included in theradiometer. Any direct sunlight which might otherwise damage theinfrared detector will then impinge also upon the light cell and theoutput therefrom is utilized to close the shutter and thereby protectthe radiation sensing element.

It is accordingly a feature of this invention to detect overheatedjournals on railways cars by employing a radiometer whose angle of scanis directed toward the hubs of passing wheels and which is also sopositioned and directed that its beam of scan includes the couplerbetween successive cars.

Another object of this invention is to provide a detection systememploying a radiometer which scans both the hubs of passing wheels andalso the wheel rims and brakes to thereby provide indications, not onlyof overheated journals, but also of dragging brakes.

An additional object of this invention isto provide a system fordetecting overheated journals on railway cars wherein a radiometer unitscans the wheel hubs of passing cars but where only a single such unitis required on each side of the trackway for both directions of traveland yet the unit is at an angle with respect to the horizontal so thatdirt and snow does not tend to accumulate on the viewing Window.

Another object of this invention is to provide a de tection systememploying a radiometer which scans both the hubs of passing wheels andalso wheel rims and brakes and employs gating circuit means which iseliective to provide separate signals for overheated journals anddragging brakes.

Another object of this invention is to provide a detection system forseparately detecting oveheated journals and dragging brakes of railwaycars which employs gating circuit means effective to distinguish betweenthe different signals received respectively from wheel hubs and r wheelrims for either direction of train movement.

Another object of this invention is to provide a detection system foroverheated journals of railway vehicles employing a protective shuttermechanism for the infrared detecting element which is automaticallyoperated in response to unusually high levels of received radiation toclose the shutter.

Other objects, purposes, and characteristic features of this inventionwill be in part obvious from the accompanying drawings and in partpointed out as the description of the invention progresses.

In describing the invention in detail, reference will be made to theaccompanying drawings in which like reference characters designatecorresponding parts throughout the several views, and in which:

FIG. 1 is a diagrammatic illustration of a railway track havingradiometers on both sides thereof and illustrating the various physicalrelationships involved in the positioning of said radiometers;

FIG. 2 is an elevational view again showing the positioning of theradiometers in respect to the wheels of a passing train and also showsthe location of the wheel detectors;

FIG. 3 is a side elevational view of a typical railway truck partiallybroken away to show the manner in which the brake shoes are included inthe line or" view along the truck as it passes such radiometers;

FIG. 4 is a side view of a radiometer;

FIG. 5 is a block diagram of the system of this invention;

FIG. 6 illustrates a shutter control circuit for the shutters of theradiometers;

FIGS. 7A, 7B, 7C and 7D when arranged with FIGS. 7B and 7D respectivelyto the right of FIGS. 7A and 7C respectively and with FIGS. 7A and 713respectively above FIGS. 7C and 7D, illustrate in a detailed manner thecircuit organization of this invention;

FIGS. 8A and 8B illustrate the amplifying circuits for a radiometerunit;

FIGS. 9A, 9B and 9C are waveform diagrams illustrating the operation ofthe circuit organization of FIGS. 7A, 7B, 7C and 7D and FIGS. 8A and813;

FIG. 10 shows an electronic track circuit organization for the controlof a track relay indicating train presence in the present invention;

FIG. 11A is a front view of an alternative form of shutter for aradiometer unit;

Fl". 11B is a partial side view illustrating the alternative shutter ofFIG. 11A;

FIG. 12 illustrates an alternative circuit for providing driving energyfor the motor of the recorder during passage of the train; and

FIG. 13 shows a typical section of recorder tape and tape transportmeans for carrying the tape.

To simplify the illustration and facilitate in the explanation, thevarious parts and circuits constituting the embodiment of the inventionhave been shown diagrammatically and certain conventional illustrationshave been employed. The drawings have been made to make it easy tounderstand the principles and mode of operation rather than toillustrate the specific construction and arrangement of parts that mightbe used in practice. The various relays and their contacts areillustrated in a conventional manner, and symbols are used to indicateconnections to the terminals of batteries or other sources of electriccurrent instead of showing all of the wiring connections to suchterminals. Thus, the symbols and indicate connections to the oppositeterminals of a source of relatively low voltage suitable for theoperation of various relays and transistor circuits; whereas, thesymbols (13+) and (B) indicate connections to the opposite terminals toa source of higher voltage particularly suitable to the operation ofvarious electron tubes and a symbol for a ground connection indicates aconnection to a voltage terminal intermediate between that of the (13+)and (B).

FIG. 1 illustrates two rails NR and SR supported by ties 11. Aradiometer RDl is located adjacent the rail NR, and a similar radiometerRD2 is located adjacent the other rail SR. Each of these radiometersscans in the direction indicated by the dotted lines 12, i.e. generallynormal to the rails. The detection of each wheel is accomplished bywheel detector units such as units WDI, WDZ, and WD3 which are shown inFIG. 1 as being physically connected to the rail SR.

FIG. 2 illustrates that the angle of scan of each radiometer asrepresented by the lines 12 is at an acute angle with the plane of theroadbed. Furthermore, the angle of scan is directed to intersect theplane of the wheels 14 and 15 at such a height that the hub of eachwheel subtencls the angle of scan asthe wheel passes through thescanning beam of the radiometer. In onder that the angle of scan canthus intersect each wheel hub, each radiometer must be so positionedthat its viewing lens is. below the level of the journal boxes IE1 and3132. An additional criterion which helps to fix the location of eachradiometer results from the desire previously mentioned that the angleof scan or viewing angle of each radiometer be also subtended by eachcoupler 16 between successive cars to thereby shield the radiometer fromhigh level solar radiation and thus obviate the need for any shutterarrangement which would otherwise be required to operate for eachpassing car. These dual requirements, namely, that the angle of scanintersect successive wheels at the lower portion of each hub and alsothat it intercept each coupler between cars, quite closely determine theangle of scan as measured with respect to the plane of the track rails,and it has been found that this angle is in the order of forty degrees.As to the distance between track rail and radiometer, it is apparentfrom FIG. 2 that it may be variable to a certain extent since distancefrom the rail is related directly to elevation with respect to the rail,i.e. the radiometer may be further from the track it it is at the sametime lowered so as to remain on the above-mentioned line of scan ofapproximately forty degrees.

Referring to FIG. 3, the horizontal dot-ted line designated 9 indicatesapproximately where the angle of scan of each radiometer intersects theplane of the outside of each wheel. From this illustration it can beseen that the angle of scan not only intersects each wheel web and hub,but also the wheel rim and the brake shoes 10 associated with therespective wheels 13 and 14. FIGS. 2 and 3 also indicate connectionsmade from the radiometers RD} and RDZ via cables and 36 respectivelywhich may be imbedded in the ballast and which conduct the signals fromsuch units to an equipment cabinet 38 which may either be positionednear one of the radiometers as shown in FIG. 2 or be located somesuitable distance away if desired.

A typical radiometer unit RDl is shown in FIG. 4 as including aninclined detector assembly D1. The detector assembly includes an opticalsystem which comprises a reflecting element 18 for focusing the heatradiation onto the infrared responsive element 20 so that an electricaloutput signal is obtained therefrom which is proportional in amplitudeto the heat radiated from the object scanned. The electrical outputsignal thus derived is transmitted over wires 42 and 43 to a plugconnector 33 and thence to associated control apparatus. In addition tothe infrared transmitting window 19 which provides protection for thedetector assembly D1, there is another window element 22 which rendersthe detector impervious to the elements and at the same time admitsinfrared energy. Directly behind this window 22 is a shutter element S1which is normally closed as shown in FIG. 4 and thus blocks the detectorassembly D1 from receiving any infrared radiation which might beimpinging upon the window 22. However, when a train is present so thatit is desired to scan the journals and brakes thereof, energy is appliedfrom the plug coupler element included therein.

33 and over wires 24 and 25 to solenoid SS1 which then causes the member26 to rotate in a counterclockwise direction to thereby wind the shutterelement S1 about element 26 and thereby move it out of its normalposition shown in FIG. 4. Rotation of the element 26 in response toenergization of the solenoid SS1 tends to tighten the spring 21 whoseone end is connected to the shaft 17 and whose other end is connected toa projection 27 on member 26. Because of this tightening of the spring21, the deenergization of the solenoid SS1 upon the passage of a trainproduces a clockwise rotation of member 26 so that the shutter S1 isrestored to the normal position between window 22 and guide 30.

A light meter LMl is also included in the radiometer unit and ispositioned alongside the detector assembly D1. This light meter includesa photo-sensitive element which provides an electrical output signalwhose amplitude is proportional to the light energy impinging thereon,and this signal is applied over wires 31 and 32 to the plug coupler 33.The use made of this signal will subsequently be described in detail,but, in brief, it may be stated that its function is to close theshutter S1 in the event that visible light, as from the sun, passesthrough the shutter having an intensity sufiicient that it might damagethe infrared detector.

GENERAL MANNER OF OPERATIGN Before proceeding with the detaileddescription of the circuit organization of this invention, a generalizeddescription will be given with reference to the block diagram of FIG. 5,the detailed circuit diagram of FIGS. 7A-7D, the waveform diagrams ofFIGS. 9A-9C, and FIGS. l3 which have already been described.

As has been mentioned, each radiometer unit supplies an output signalwhose amplitude is proportional to the level of infrared radiationimpinging upon the detector Because the angle of scan is directed in themanner described above, the radiometer output signal has its amplitudesuccessively proportionate to the temperature of each passing wheel hub,and also each wheel web and rim. Thus, the output of one of theradiometer units such as the unit RD2 may appear as shown in the topmostline of the waveform diagrams of FIGS: 9A, 9B or 9C, depending upon theparticular conditions encountered. When the journals associated withsuccessive wheels are at normal operating temperatures, the radiometeroutput signal may appear as indicated in FIG. 9A which shows that theoutput increases only slightly as successive wheel hubs are scanned.FIG. 9B shows the output of the radiometer when one of the two journalson one side of a car truck is at an abnormally high temperature; theradiometer signal is shown as increasing markedly above its normalamplitude. FIG. 9C shows how the output signal of the radiometer unitRD2 may appear when the brakes associated with the wheels of the truckare both dragging. The radiometer unit receives a high level ofradiation not only from the wheel hubs which are heated as a result ofthe conduction of heat from the wheel rims, but also receives evenhigher levels of radiation from the wheel rims which are directly heatedthrough frictional contact with the brakes. The asymmetrical nature ofthe waveforms of the two successive wheels of the single truck as shownin FIG. 9C is readily explainable by the aid of FIG. 3 which shows thatfor each wheel of the truck, the brake is toward the center of thetruck, and it is natural that the temperature on the center side of eachwheel should be higher than on the opposite side since the formertemperature reading is affected by the presence of the brake shoe itselfwhich maybe at an even higher temperature than the wheel rim.

The foregoing description shows that the output of the radiometer unitis a composite signal in that itrepresents the temperature of whateveris being scanned any instant and that it may go to a high value, notonly when an overheated journal is being scanned, but also foroverheated wheel rims or, for that matter, for any other source ofinfrared radiation emanating from a passing vehicle. This demonstratesthe need for using gating circuits so that the output signal of theradiometer will, in effect, be interrogated to determine whether anoverheated journal condition exists only at the very instant that thebeam of scan of the radiometer units includes the wheel hub of a passingtruck. Likewise, the gating circuitsmust be elfective to interrogate theradiometer output signal to determine whether a dragging brake conditionexists only at the particular instant that the beam of scan of the unitincludes the rim of each wheel.

Various detection devices may be used to control the gating circuits sothat each radiometer unit will have its output signal interrogated atthe desired times. To effect this result, it has been found practical toprovide a track instrument, affixed to the track rail or rails, whichprovides an accurate indication as to the relative position of eachpassing wheel with respect to the radiometer unit. The particular trackinstrument illustrated in the accompanying drawings and which has beenfound to work well in practice, employs a permanent magnet with anassociated iron core coil affixed to the track rail at a preselectedlocation. As the wheel flange passes through an inductive couplingrelationship with the coil, there is a distinctive change in the fluxwhich is provided by the permanent magnet and which links with the turnsof the coil. Because of this, a voltage is induced in the coil, and thisvoltage is applied to an associated electronic circuit and acts thereonto cause it to apply a distinctive output pulse of uniform amplitudes tothe associated gating circuits.

FIG. 1 shows that two such wheel detector units WD1 and WD2, are aflixedto one of the track rails, each being substantially equidistant from theintersection with the track rail of a vertical plane through the beam ofscan of the radiometer unit RD2 as indicated by the dotted lines 12. Afurther wheel detector unit WD3 is affixed to the same track rail and isspaced from the unit WD2 by a distance greater than the distance betweenthe units WD1 and WD2. The units WD1 and WD2 are so positioned that inthe time between successive output pulses from the wheel detector unitsWD1 and WD2 as a single wheel passes between these two detector units insuccession, the beam of scan of the radiometer unit RD2 passes over theentire hub of that wheel. From this, it is clear that the associatedgating circuit should, during this interval, interrogate the output ofradiometer unit RD2 to ascertain whether its output signal is at a highlevel indicative of an overheated journal condition so that adistinctive signal should be given. This interrogation effected by thegating circuits should take place irrespective of the order in which theoutput signals from the units WD1 and WD2 are received, i.e. theinterrogation should be properly effected for either direction of traintravel. It will subsequently be described how this result is achieved.

During the time that each wheel is between the detector units WD2 andWDS, the angle of scan of the radiometer unit RD2 no longer includes thehub of that wheel but is now instead scanning the web and rim of thatwheel. If it is assumed that the truck of FIG. 3 is passing along therails of FIG. 1 in a directiontfrom left to right, it can be realizedthat, when the center of wheel 14 lies between wheel detector units WD2and W133, the angle of scan of radiometer unit RD2 includes that portionof wheel 14 lying between the center thereof and the center of the truckso that not only the wheel web and rim but also the brakeshoe 10 is thenbeing scanned. As this truck proceeds further along the track rails sothat the center of wheel 13 lies between wheel detector units WD2 andWD3, the angle of scan of radiometer RD2 then includes that portion ofwheel 13 lying between the center of the Wheel and the outermost,lefthand end of the truck and thus does not include the brakeshoe 19associated with wheel 13 but it does include the Wheel rim. Thus, withrespect to each wheel, as its center passes along the portion of railbetween detector units W332 and WD3, the wheel rim is being scanned; foralternate wheels, the brakeshoe is also included within the angle ofscan, whereas for the remaining alternate wheels the brakeshoe is notincluded. When there is a dragging brake condition, the inclusion of theheated brakeshoe results in a greater output signal from the radiometerunit, but the dragging brake condition so elevates the wheel rimtemperature that an entirely adequate determination of this conditioncan be made merely by scanning the wheel rim without including thebrakeshoe as well in the angle of scan.

From the description previously given, it can now be realized that thegating circuit which interrogates the output of the detector unit toascertain whether or not there is a dragging brake condition, iscontrolled by the output of the wheel detector units WDZ and W133. Thisgating circuit is rendered active throughout the time between successiveoutputs from these two detector units W132 and WDS, and this gatingcircuit is effective also irrespective of the order in which theseoutput signals from the wheel detector units are received so that properoperation is achieved for either direction of travel.

In summary, the gating circuits which efi'ect separate interrogation ofthe radiometer output signal to detect both overheated journal anddragging brake conditions are effective for either direction of travel.One gating circuit interrogates the radiometer output for a draggingbrake condition as to each wheel throughout the time the center of thatwheel lies between detector units W132 and WDS, and a second gatingcircuit interrogates the radiometer output during the time the center ofthat same wheel lies between the detector units WDl and WDZ.

Where the two radiometer units for the two sides of a train are directlyopposite each other as shown in FIG. 1, the gating circuits may be usedin common for both and only one set of wheel detector units need beemployed to control the gating circuits. It is, of course, within thescope of this invention that there be different sets of wheel detectorunits for the two different track rails, and where this is done they maybe either placed directly opposite each other or not, as is desired.Where they are not opposite each other, difierent gating circuits may beused for the different radiometers, and these radiometers then also neednot be placed directly opposite each other. The arrangement of FIG. 1 isordinarily preferred, however, because of the simplicity and economy ofapparatus which it entm'ls. However, even where the arrangement of FIG.1 is desired with the radiometer units directly opposite each other andwith only one set of three wheel detector units being used, it should berecognized that it is not a requirement that all the wheel detectorunits be on the same rail; the gating circuits will operate in asatisfactory manner and in accordance with the description given whetherthey are on the same or on difierent rails.

The output of each radiometer is a low-level, unidirectional outputvoltage, and this must be substantially amplified in order to be of use.The common technique of DC. amplification is employed in the presentinvention by providing a chopper and square wave generator such as thechopper 78 and square wave generator 79 illustrated in FIG. 5 as beingassociated with the radiometer RDl. The function of the chopper is toamplitude modulate the square wave of voltage of the square wavegenerator 79 according to the amplitude of the unidirectional outputsignal of the radiometer unit. The output of the square wave generatoris a square wave of constant amplitude whose frequency i such that asubstantial number of output cycles are included within the id durationof each voltage variation provided by the radiometer. The result of thisis that the A.C. amplifier 89 receives an input signal which is analternating voltage at the frequency of the square wave generator '79,and this alternating signal is amplitude modulated in accordance withthe amplitude of output of radiometer DRl. The amplifier 89 provides therequired amplification of this signal and supplies its output to twogating circuits 82 and 83. As will subsequently be discussed. in detail,gating circuit 82 receives a gating voltage only throughout the timethat the radiometer R131 is scanning the hub of each passing wheel, i.e.only wmle the center of each wheel lies between the wheel detector unitsWDl and WD2. On the other hand, gating circuit 83 receives a gatingvoltage only throughout the time that the beam of scan of radiometer RDlincludes the wheel web and rim of each passing wheel, i.e. this gatingvoltage is applied only throughout the time each wheel center liesbetween the wheel detector units WD2 and WD3.

Each gating circuit 82 or 83 can transfer its input signal received fromamplifier 8%) to a respective diode detector circuit 87 or 83 only whenit receives the required gating voltage. It follows, therefore, that thediode detector circuit 8'7 receives a signal representing the output ofamplifier so during the brief interval that radiometer RDl is scanningthe hub of a passing wheel. This wheel hub signal is rectified andfiltered by the diode detector circuit 87 so that an output signal isprovided which corresponds to the output of radiometer RDl throughoutthis gating interval and essentially differs therefrom only in that itis substantially amplified. Thissignal is applied to the hot journaldetection circuit 93. If its amplitude is above some predetermined valueso that the particular wheel hub causing it must have been at adangerously elevated temperature, the hot journal detection circuit 93will produce an output signal which is then applied to the inverter 99and thence to the signal circuit 97 Where it is effective to give adistinctive signal. The output signal of the diode detection circuit 87is also applied directly to one of the analog pens included in therecorder of FIG. 7B and deflects this pen according to its amplitude.Because of this, the analog pen is deflected for each passing wheel byan amount representative of the infrared radiation emanating from itshub; an examination of the resulting trace provided by the pen indicateswhich of the journals, if any, are operating at unduly hightemperatures.

In an analogous manner, the gating circuit 83 causes the output ofamplifier 8G to be applied to the diode detector circuit 88 only whenthis gating circuit 83 receives a gating voltage from the FFZ flip-flopcircuit as, i.e. throughout the time that the center of each wheel liesbetween the wheel detector units WDZ and WDS. The diode detector circuit88 rectifies and filters the resulting signal representing the level ofradiation received from the wheel rim and supplies it as one input tothe dragging brake detection circuit 94.

The dragging brake detection circuit 94 not only receives this lattersignal representative of the temperature of the wheel rim, but alsoreceives the output signal of the diode detection circuit 87representing wheel hub temperature. Both these signals are stored for abrief interval in this dragging brake detection circuit 94 until aninput signal is received from the clear circuit 1&5 at which time acomparison is made of their respective levels. If the stored signalrepresenting wheel hub temperature is greater than the stored signalrepresenting wheel rim temperature, this is an indication that the wheelrim is at an elevated temperature merely because of the conduction ofheat to it from the wheel hub so that there is in fact no dragging brakecondition. At such times, no output signal is applied to the No. 1marker pen in the recorder. However, if at the time of comparison, thesignal representing wheel rim temperature is greater than thatrepresenting wheel hub temperature, this is an indication that the wheelrim is at an elevated temperature because of dragging brakes and then anoutput signal is applied to the No. 1 marker pen to indicate thiscondition.

When the above comparison has been made and prior to the arrival of thenext Wheel, the clear circuit 105 acts to erase from the dragging brakedetection circuit 94 the voltages stored therein as a result of thepassage of the preceding wheel. This clearing out of the dragging brakedetection circuit 94 results in its being able to store such voltagesagain for thenext wheel.

The above description has been given with particular reference made tothe manner in which the output of the radiometer RDI is utilized to givedetection of both dragging brakes and overheated journal. Analogous circuit means is shown which causes the output of the other radiometer RD2to be acted upon in the same way so that different distinctiveindications may be given when such conditions are detected on the otherside of each passing train.

The gating voltages referred to above are derived from the two flip-flopcircuits FBI and FF2 shown in both FIG.

'each successive wheel has its center between the WD1 and WDZ detectorlocations and that the flip-flop FFZ .similarly provides its gatingvoltage throughout the interval that each successive wheel has itscenter lying within the stretch of track between the two detectorlocations WDZ and WD3.

A relay R is also provided and is controlled by a control circuit 68which receives its input from the flip-flop EFL As a train passes theradiometer locations, the flipflop FFl is operated for each passingwheel to the con dition wherein it provides the required gating voltageas already described. At all other times, when it is not pro viding thisgating voltage it is in its opposite condition, and the result,therefore, is that this flip-flop *FFI operates alternately betweenopposite states, going through a complete cycle from one condition tothe other and then back again for each passing wheel. This intermittentoperation of the flip-flop FFI effects a control through contact 62 ofrelay D onto the control circuit 68 causing it to pick this relay R up.This condition of relay R indicates that a train is present. When thetrain has passed, the iiip-flop FF1 is no longer operated betwetenalternate states, and the control circuit 68 senses this and thenpermits the relay R to be restored to its normal dropped-away condition.

One use that is made of relay R is to provide a resetting of the twoflip-flops 'FFl and FF2 after each train has passed. Thus, closure ofback contact 71 vsuddenly grounds the lower terminal of capacitor 73 andthis has the effect, as will subsequently be shown, of operating each ofthe flip-flops FFI and FFZ to a normal condition.

Another use made of the operation of relay R involves the front contact77 of this relay. When this front contact closes upon the arrival of atrain at the radiometer location, electrical energy is applied throughthe contact to the recorder to set it into operation. With reference toFIG. 13, the recorder is illustrated as having transport means includinga motor 129 and a drum 130 for feeding a tape 131 under a plurality ofanalog pens '134 and a plurality of marker pens137.

An additional function of relay R resides in its control of relay D.This latter relay is, in effect, a direction sensing relay in that it ispicked up for one direction of travel of a passing train but not for theother. The exact manner in which the contacts 70 and =74 of relay Reffect the desired control of relay D will be more readily understoodwhen the detailed circuits of FIGS. 7A7D are described. As to thefunction of the latter relay D, its purpose is to a cause the outputs ofthe two flip-flops F1 1 and FF2 to be 'of each train as will also moreeasily be understood when the detailed circuits are described below.

Still another function of relay R involves its control of relay SCR bymeans of which the shutters on the radiometers are actuated. Thiscontrol is illustrated in FIG. 6 which shows a track circuit includingthe track rails SR and NR and defined by the insulated joints 109-412.The track circuit is energized by a battery 114 which supplies currentto the track rails through limting resistor 115. Track relay TR isconnected across the track rails at the opposite end of the tracksection and is normally energized by the current flowing in the trackrails but is dropped away whenever a train occupies the track sectionand shunts the track rails.

The shutter control relay SCR is energized by a pickup circuit includingfront contact of relay R so that relay SCR is picked up whenever relay Ris energized upon the passage of a train. A stick circuit is provided tomaintain the relay SCR picked when once picked up through a circuitwhich extends from and includes back contact 117 of track relay TR, backcontact 1 18 of the light relay LR, front contact 119 of relay SR, andthrough the winding of this relay SCR, to the terminal. Relay LR isnormally dropped away so that when relay R picks up upon the passage ofa train and, thereby picks up relay SCR as previously described, thisstick circuit is completed through the back contact 117 of track relayTR which is then dropped away in response to the presence of a train inthe track section. Ordinarily, it is not until the train has vacated thetrack section so that track relay TR can be restored to its normalpicked-up condition that energy is removed from the windin g of relaySCR. However, under certain conditions a high level of radiation, asfrom the sun, may fall upon the interior of the radiometer in theinterval after the train has passed but before the track relay picks up.If this happens, the light meter element such as LM2 provides a reducedresistance in series with battery 121 so that relay LR picks up, andopens back contact 118 so that relay SCR is deenergized. From thisdescription, it can be seen that front contact 123 of relay SCR isoperated to a closed condition to thereby energize solenoids SS]. andSS2 only upon the passage of the first wheels of the passing train whicheffects the picking up of relay R, and this energization of thesolenoids is maintained until the track section becomes againunoccupied, so that relay TR is again picked up, except that when a highlevel of radiation impinges upon the detecting elementts as from directsunlight, then relay SCR is released immediately after the passage ofthe train so that its front contact 123 will open and thereby deenergizethe solenoids and permit the shutter to be restored to its normalprotective position.

In describing the general mode of operation of the flipflops FBI andFFZ, reference will be made not only to the block diagram of FIG. 5, butalso to the detailed circuits of FIGS. 7A-7D, particularly FIGS. 7A and7B.

The two flip-lop circuits FFl and FFZ respectively provide the twogating voltages previously mentioned, the gating voltage provided byflip-flop FFI existing throughout the time that the center of each wheellies between the wheel detectors WDl and WD2, when the radiometer isscanning the associated wheel hub, and the flip-flop FF2 providing itsgating voltage throughout the time each wheel center lies between wheeldetectors WDZ and WD3 at which time the associated radiometer isscanning the wheel rim of the associated wheel. These flip-flop circuitsare operated by the respective wheel detection circuits. Thus, as eachwheel flange passes into and then out of an inductive couplingrelationship with the permanent magnet 47 associated with a particularwheel detector, a voltage pulse is generated which causes the associatedthyratron such as thyratron T1 in the wheel de- .tector circuit 55 tofire and provide a negative-going plate voltage pulse to the associatedflip-flop circuit. The output of the thyratron T1 associated with wheeldetector WDl is provided as an input only to the flip-flop FFl, and thethyratron T3 similarly associated with wheel detector WD3 supplies itsoutput pulse only to the flip-lop FFZ. On the other hand, the thyratronT2 associated with wheel detector WD2 provides its output pulse to boththe flip-flops FFI and FFZ.

For a train traveling from left to right and causing output pulses to beprovided in succession by the thyratrons T1, T2 and T3, in that order,each output pulse from thyratron T1 operates flip-flop FF! to thecondition where it will provide the desired wheel hub gating voltageover wire 292 to the gating circuits S2 and 84. The output pulse fromthyratron T2 which'is applied to flip-flop FF operates this flip-flopFFI to the opposite condition where it no longer provides this gatingvoltage. At the same time, this output pulse from thyratron T2 operatesflip-lop FF2 to the condition where it will provide the desired wheelrim gating voltage over wire 229 to both the other remaining gates 83and 85. The end of this latter gating voltage is demarcated by theoccurrence of the output pulse from thyratron T3 which operates flipfiopP1 2 to the condition where this gating voltage is removed. These gatingvoltages obtained from the flip fiops F1 1 and FFZ respectively areapplied to the wires 292 and 229 through back contacts 62 and 63 ofdirection sensing relay D respectively, which relay is dropped away forthis particular direction of travel as will subsequently be described.

For the opposite direction of travel, each successive wheel causes anoutput pulse to be produced first by thyratron T3, and this pulseoperates flip-lop FFZ to the condition where it will provide'therequired wheel rim gating voltage. (It will later be described that forthe very first wheel of the train, the operation of the fiip-flopsdiifers somewhat from that described here, but such preconditioningaction is of no effect after the first wheel has passed and so will notbe further considered at this time.) The termination of this gatingvoltage is brought about by the subsequent operation of flip-flop FF2when the next-occurring output pulse is derived from the plate ofthyratron T2. The detailed description that follows these particularcircuits will make it evident that the actual condition of flip-flop FFZduring the time that each wheel center lies between the wheel detectorsWD2 and WD3 is entirely dependent upon the direction of travel of thatwheel. More specifically, for the left to right direction of travel, theflip-flop FFZ will be in the condition where its tube A is conductivethroughout the time that the wheel center lies between detector WD2 andWD3, but the opposite conditions prevail, i.e. tube B is conductive fora train traveling from right to left throughout the time that each wheelcenter lies between wheel detectors WD2 and W133. In either case,however, the flip-flop circuit provides the desired gating voltage, andit is for this reason that the contact 63 of relay D must be provided.More specifically, this contact of the direction sensing relay permitsthe connection of wire 229 to the cathode of tube A whenever thedirection of travel of the train is from left to right, but insteadconnects this wire through front contact 63 to the cathode of tube B forthe opposite direction of travel. In this manner, even though theflip-flop FF2 is in different states, one the opposite of the other,during the time that it is to provide its output gating voltage,dependent upon the direction of travel of the train, the directionalrelay D ensures that the desired gating voltage will nevertheless beobtained from the flip-fiop.

The above description given with respect to flip-flop FFZ applies aswell to fip-fiop FF 1 in the sense that this flip-flop FFI is in theexact opposite state when it is to be effective to supply the hub gatingvoltage for a train traveling from right to left as compared to thepreviously described condition wherein the train was traveling from leftto right. Here again, however, the contact 62 of relay D properlyconnects the wire 292 to either the cathode of tube A or to the cathodeof tube B in accordance with such direction of travel so that thedesired gating voltage may be applied to gates 32 and 9- regardless ofthe direction of travel.

DESCRIPTION OF DETAILED CIRCUITS Amplifier and gating circuits: FIGS.8A-8B FIGS. 8A and 8B when placed with P16. 83 to the right of PEG. 8Aillustrate the manner in which the unidirectional output signal of theradiometer is amplified by means of a chopper, square wave generator,A.C. amplifier and gated detection circuits. The circuits shown arethose which are associated with a single one of the radiometer units;similar circuits are, of course, provided for the other radiometer unitbut will not be described in detail.

The square wave generator 79 may be of any conventional type and mayemploy two transistors Q4 and Q5 as illustrated in FIG. 8A. Essentiallythe square wave generator is a self-runnin oscillator wherein the twotransistors are alternately and oppositely operated between theircut-olf and conductive conditions so that a square wave of voltageappears in the primary winding of transformer TRZ included in thechopper 78. This square wave of voltage alternately renders the twotransistors Q6 and Q7 increasingly conductive and since the collector oftransistor Q6 is further influenced by the level of the radiometersignal applied to it through capacitor 167, the over-all result is thatthere is applied, through capacitor 153, and impressed upon resistor169, an alternating voltage having a frequency corresponding to thefrequency of operation of the square wave generator, but with itsamplitude varying in correspondence with the amplitude of theunidirectional output provided by the radiometer unit.

This AC. voltage appearing across resistor 169 is amplified by thetransistor amplifiers stages comprising trausistors Q8, Q5, Q10 and Q11all included in block 80 of FIG. 8A. The result is that there appearsbetween the collector of transistor Q11 and ground an AC. voltage whichis an amplified version of that appearing across the previouslymentioned resistor 169. This AC. voltage is applied to the primarywinding of transformer TR3 and induces a corresponding AC. voltage inthe secondary windings of this transformer.

The/separate secondary windings of transformer TR3 are each includedwith the respective transformers TR4 and TRS in the gating circuits 84-and 85 respectively. In the description that follows, reference will bemade particularly to the gating circuit 84, and this description Will beequally applicable to the other gating circuit 85 which is identicalthereto.

The gating voltage that is applied to the center tap of the primarywinding of transformer TR4 is obtained from the flip-flop FF]. and isderived, as described above, from a cathode resistor. When this tube isnonconductive, zero voltage is applied to the primary of transformerTR4. Since a positive voltage is at all times obtained from the junctionof resistors 201 and 202 and applied to the center-tap of the secondarywinding of transformer TRS, the left-hand terminal each of therectifiers 1%7 and 198 is at a more positive potential than itsright-hand terminal so that each of these rectifiers is blocked and noconduction can take place through them. Therefore, none of the A.C.voltage appearing across the secondary winding of transformer TR3 can beapplied to the primary winding of transformer TR4. However, when theelectron tube A included in the flip flop FFI becomes conductive so thatthe voltage across the cathode resistor is raised above ground, thepotential

8. A SYSTEM FOR DETECTING AND REGISTERING THE OVERHEATING OF EITHER OFTWO PORTIONS OF A WHEEL OF A RAILWAY CAR UPON PASSAGE OF THE CAR ALONG ASTRETCH OF RAILWAY TRACK COMPRISING, (A) DETECTOR MEANS DISPOSED AT APOINT ALONG SAID STRETCH OF TRACK HAVING AN ELEMENT SENSITIVE TOINFRARED RADIATION AND HAVING MEANS FOR IMAGING UPON SAID ELEMENT DURINGTHE PASSAGE OF THE CAR THE INFRARED RADIATIONS EMITTED BY SAID WHEELWHILE SCANNING A PLURALITY OF DIFFERENT RADIAL PORTIONS OF SAID WHEEL ATA PREDETERMINED ELEVATION LEVEL INCLUDING A PORTION OF THE WHEEL HUB,SAID DETECTOR MEANS BEING OPERABLE TO GENERATE A SIGNAL CONTINUOUSLYVARIABLE IN ACCORDANCE WITH THE DEGREE OF HEAT OF THE PORTION OF THEWHEEL BEING SCANNED, (B) GATING MEANS INCLUDING WHEEL DETECTORS SUBJECTTO ACTUATION BY SAID CAR WHEEL FOR FORMING FIRST AND SECOND GATINGINTERVALS FOR REGISTRATION OF TEMPERATURES OF FIRST AND SECOND OF SAIDRADIAL PORTIONS OF SAID CAR WHEEL RESPECTIVELY AS DETECTED BY SAIDDETECTOR MEANS, (C) STORAGE MEANS FOR STORING THE SIGNAL CORRESPONDINGTO THE TEMPERATURE OF SAID FIRST RADIAL PORTION UNTIL AFTER REGISTRATIONOF THE TEMPERATURE OF SAID SECOND RADIAL PORTION, (D) MEANS FORCOMPARING THE SIGNAL INDICATIVE OF THE TEMPERATURE OF SAID FIRST ANDSECOND RADIAL PORTIONS OF THE WHEEL, AND (E) MEANS CONTROLLED BY SAIDCOMPARING MEANS FOR REGISTERING WHICH OF THE TWO RADIAL PORTIONS HAS THEHIGHEST TEMPERATURE.